Question: Christopher is 12 years younger than Gabriela. Gabriela and Christopher first met 3 years ago. Twelve years ago, Gabriela was 5 times older than Christopher. How old is Gabriela now?
We can use the given information to write down two equations that describe the ages of Gabriela and Christopher. Let Gabriela's current age be $g$ and Christopher's current age be $c$ The information in the first sentence can be expressed in the following equation: $g = c + 12$ Twelve years ago, Gabriela was $g - 12$ years old, and Christopher was $c - 12$ years old. The information in the second sentence can be expressed in the following equation: $g - 12 = 5(c - 12)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $g$ , it might be easiest to solve our first equation for $c$ and substitute it into our second equation. Solving our first equation for $c$ , we get: $c = g - 12$ . Substituting this into our second equation, we get the equation: $g - 12 = 5($ $(g - 12)$ $ -$ $ 12)$ which combines the information about $g$ from both of our original equations. Simplifying the right side of this equation, we get: $g - 12 = 5g - 120$ Solving for $g$ , we get: $4 g = 108$ $g = 27$.